1. Field of the Invention
The present invention is broadly concerned with oligomers capable of inhibiting expression of interleukin genes, transcription-inhibiting complexes, each composed of an oligomer bound to an interleukin gene, and corresponding methods having potential as therapies for inflammatory polyarthropathy. More particularly, in preferred embodiments, each of these oligomers binds in the parallel or antiparallel orientation to the polypurine strand of a polypurine-polypyrimidine region of the transcribed region of an interleukin gene, thereby resulting in the formation of a transcription-inhibiting triplex.
2. Description of the Prior Art
Interleukin-15 is a novel cytokine having biological functions similar to those of interleukin-2 even though there is no significant sequence homology between the two. Interleukin-15 is produced by epithelial and fibroblast cell lines, and by peripheral blood monocytes. Furthermore, interleukin-15-specific mRNA has been found in several normal human tissues including placenta, skeletal muscle, and kidney (Grabstein et al., 1994, Science 264:965-968).
Interleukin-15 induces T-cell proliferation, enhances natural killer (NK) cell cytotoxicity and antibody-dependent cell-mediated cytotoxicity, and upregulates production of NK cell-derived cytokines including interferon-.gamma. (FIN-.gamma.), granulocyte/macrophage-colony-stimulating factor (GM-CSF), and tumor necrosis factor-.alpha. (TNF-.alpha.) (Grabstein et al., 1994, Science 264:965-968; Burton et al., 1994, Proc. Natl. Acad. Sci. 91:4935-4939; Bamford et al., 1994, Proc. Natl. Acad. Sci. 91:4940-4944; Giri et al., 1994, EMBO J. 13:2822-2830; Carson et al., 1994, J. Exp. Med. 180:1395-1403; and Giri et al., 1995, EMBO J. 14:3654-3663). Interleukin-15 also costimulates proliferation and differentiation of B cells activated with anti-immunoglobulin M (anti-lgM) (Armitage et al., 1995, J. Immunol. 154:483-490), stimulates locomotion and chemotaxis of normal T cells (Wilkinson et al., 1995, J. Exp. Med. 181:1255-1259), and promotes interleukin-5 production by T cells which may contribute to eosinophilic inflammation (Mori et al., 1996, J. Immunol. 156:2400-2405). Persistant eosinophilic inflammation in the bronchial mucosa is well recognized in the pathogenesis of chronic asthma (Bousquet et al., 1990, N. Engl. J. Med. 323:1033).
Rheumatoid arthritis is a destructive inflammatory polyarthropathy (Maini et al., 1995, in Mechanisms and Models in Rheumatoid Arthritis, pp. 25-26, eds. Henderson, Edwards, and Pettifer, Academic Press, London, 25-26). Chronic rheumatoid synovitis is characterized by the presence of activated fibroblast-like synoviocytes together with infiltration of the normally acellular synovial membrane by macrophages, T cells, and plasma cells (Duke et al., 1982, Clin. Exp. Immunol. 49:22-30). Levels of interleukin-15 in rheumatoid arthritis synovial fluid are sufficient to exert chemoattractant activity on T cells in vitro, and can induce proliferation of peripheral blood and synovial T cells; furthermore, interleukin-15 induces an inflammatory infiltrate consisting predominantly of T lymphocytes (McInnes et al., 1996, Nature Medicine 2:175-182). Therapies directed at T cells, such as cyclosporin A and monoclonal antibodies against T-cell surface antigens, produce significant clinical improvement, confirming the importance of T cells in inflammatory polyarthropathy (Horneff et al., 1991, Arth. Rheum. 34:129-140; Wendling et al., 1991, J. Rheumatol. 18:325-327; Harrison et al., 1992, in Second-line Agents in the Treatment of Rheumatic Diseases, eds. Dixon and Furst, Dekker, New York). Thus, it appears that interleukin-15 plays a significant role in T-cell recruitment and activation in inflammatory polyarthropathy.
Oligomers (i.e., oligonucleotides and oligonucleotide analogs such as protein nucleic acid) are reagents for inhibition of gene expression because of their high-affinity binding to specific nucleotide sequences. The best known strategy for causing inhibition of gene expression involves antisense oligonucleotides which bind to mRNA to inhibit its processing or translation. For example, it has been shown that the expression of the human .alpha.1 (I) collagen gene is effectively inhibited by antisense oligonucleotides targeted at specific regions of the .alpha.1 (I) mRNA (Laptev et al., 1994, Biochemis-try 33:11033-11039).
Additionally, gene promoters can serve as targets for a novel, antisense strategy, namely the triplex strategy. This strategy employs single-stranded oligomers that bind to the major groove of a polypurine-polypyrimidine region of a double-stranded DNA to form a triplex in a sequence-specific manner. These oligomers are called triplex-forming oligonucleotides (TFO's) or TFO analogs. In a polypurine-polypyrimidine region, a purine-rich DNA single strand is hydrogen bonded by Watson-Crick base-pairing to a pyrimidine-rich DNA single strand; the polypurine-polypyrimidine region is not necessarily a homopurine-homopyrimidine region in that the purine-rich DNA single strand may contain at least one pyrimidine residue and the pyrimidine-rich DNA single strand may contain at least one purine residue. These triplexes have been shown to inhibit transcriptional activity of various promoters in both in vitro and in vivo experiments (Grigoriev et al., 1992, J. Biol. Chem. 267:3389-95; Cooney et al., 1988, Science 241:456-59; Maher et al., 1989, Science 245:725-30; Ing et al., 1993, Nucleic Acids Res. 21:2789-96; Kovacs et al., 1996, J. Biol. Chem. 271:1805-1812). However, the use of oligomers to inhibit transcription of interleukin genes and to thereby suppress T-cell recruitment and activation as a method of treating inflammatory polyarthropathy is unknown in the prior art.